In petroleum forecourt installations, pipework running between dispensing pumps and a subterranean fuel storage tank passes into a manhole chamber which is situated directly above the manhole lid of the tank. The chamber is normally defined by an upstanding wall which, when viewed from above, can be of an octagonal, square or rectangular shape, and which includes apertures through which respective pipes pass.
It is desirable to provide a seal between each of the apertures and its respective pipe to avoid ingress of water into the manhole chamber. To that end, it is known to attach a fitting to a portion of the wall around the aperture and a rubber “boot” that sleeves over the pipe and is clamped to both the pipe and the fitting by, for example, jubilee (TM) clips. Some types of fitting are bolted to the chamber wall, whilst other types of fitting provide inner and outer parts between which the wall is sandwiched, the inner and outer parts being held together by a screw-threaded connector which extends through the aperture. These connectors often incorporate a rubber seal located between a part of the connector and the chamber wall.
An example of a prior art seal is described in U.S. Pat. No. 5,538,035. This illustrates a flanged fitting for a subterranean tank. The flanged fitting is attached to the side of the tank by ultrasonic welding or a chemical bonding agent. Whilst heat sealing is referred to as a method of attachment, if heating is used then it must be applied using an external source of heat.
Heat sealable connections are known per se. For example U.S. Pat. No. 5,601,315 describes a plastic moulded connector for connecting a plastic branch pipe onto a plastic pipeline, comprising a saddle portion and a pipe socket portion. Both the saddle and pipe portions contain electric heating windings. However, the configuration of this coupling makes it entirely unsuitable for the present application.
Neither type of fitting provides a completely effective seal.
Consequently, both types of seal can allow water to leak into the manhole chamber and to accumulate in a pool in the bottom of the chamber. This in turn makes the maintenance of the chamber bottom and tank entrance extremely difficult.
Furthermore, it has been found that the removal and replacement of the rubber seals of conventional arrangements can also be extremely difficult and expensive.
It is an object of the present invention to provide a fitting which overcomes some or all of the above disadvantages.